help with 16 port SMC hub to jack jack to computer problem

On Sun, 28 Mar 2004 08:24:27 GMT, CJT <abujlehc DeleteThis @prodigy.net> wrote:

 >Roscoe Pendoscoe wrote:

  >>
  >> Roscoe
 >
 >Yes, normally one would use a straight-through cable (if I understand
 >the question correctly).
 >
 >Make yourself a crossover cable and try using that to connect from
 >the computer to the wall jack. If you suddenly have connectivity,
 >you know you've mixed 568-A and 568-B (i.e. the diagram on the jack
 >and the alternate) in the wall. Otherwise you can use either, as long
 >as you're consistent (use the same at both ends).

I am going back today (no witnesses to my ineptitude) Sunday.

Actually, before leaving in disgust and frustration, I did make a
crossover cable and plugged into wall jack, then computer and did get
2 lights lit. Activity? (yellow) and bottom green. Both are constant
non-blinking.

Would that indicate a mixed 568A to 568B? I am pretty certain it is in
fact mixed.

The Hubbell modular jack does have a second color pin-out scheme it
seems. If not, I think making a 568A cable end at the hub end to
match the jack might be easier than guessing at the jack end if
there's not an alternate pin-out scheme on the jack.

Problem there though is I'd be mixing MY 568A with ALL EXISTING that
are 568B. I just need this to work by tomorrow AM when the fellow who
inhabits this office who happens to be head of the company. He's been
gone a week and they redid his office, painting, new desk layout and
wire clutter gone.
 >
 >A common mistake is to untwist too much, but that won't normally
 >totally destroy connectivity -- it'll just increase the error rate.

How much is too much, untwist-wise?

Thanks,

Roscoe<!-- ~MESSAGE_AFTER~ -->
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Roscoe Pendoscoe wrote:

 > On Sun, 28 Mar 2004 08:24:27 GMT, CJT <abujlehc DeleteThis @prodigy.net> wrote:
 >
 >
  >>Roscoe Pendoscoe wrote:
 >
 >
   >>>Roscoe
  >>
  >>Yes, normally one would use a straight-through cable (if I understand
  >>the question correctly).
  >>
  >>Make yourself a crossover cable and try using that to connect from
  >>the computer to the wall jack. If you suddenly have connectivity,
  >>you know you've mixed 568-A and 568-B (i.e. the diagram on the jack
  >>and the alternate) in the wall. Otherwise you can use either, as long
  >>as you're consistent (use the same at both ends).
 >
 >
 > I am going back today (no witnesses to my ineptitude) Sunday.
 >
 > Actually, before leaving in disgust and frustration, I did make a
 > crossover cable and plugged into wall jack, then computer and did get
 > 2 lights lit. Activity? (yellow) and bottom green. Both are constant
 > non-blinking.

That sounds like a connection to me. Precisely what the lights mean
depends on the particular device (and I'm not familiar with yours),
although I've seen yellow mean negotiation at 10 Mbps (rather than 100)
on some of my switches. Often there's a link light and a combined
speed/activity light.

 >
 > Would that indicate a mixed 568A to 568B? I am pretty certain it is in
 > fact mixed.

All a crossover cable is, is a 568B on one end and a 568B
on the other. An even number of crossovers in series is
equivalent to a straight-through (kinda like double negation).
All that matters to the equipment is that you have the right
ultimate connectivity (x-over or straight), although to avoid
confusion for those who follow, it's best to keep all but a
final drop cable straight-through, and to clearly label all
crossovers.

 >
 > The Hubbell modular jack does have a second color pin-out scheme it
 > seems. If not, I think making a 568A cable end at the hub end to
 > match the jack might be easier than guessing at the jack end if
 > there's not an alternate pin-out scheme on the jack.
 >
 > Problem there though is I'd be mixing MY 568A with ALL EXISTING that
 > are 568B. I just need this to work by tomorrow AM when the fellow who
 > inhabits this office who happens to be head of the company. He's been
 > gone a week and they redid his office, painting, new desk layout and
 > wire clutter gone.
 >
  >>A common mistake is to untwist too much, but that won't normally
  >>totally destroy connectivity -- it'll just increase the error rate.
 >
 >
 > How much is too much, untwist-wise?

I try not to untwist any more than necessary; I think you can achieve
under 3/8 inches. I frankly don't know whether there's a spec on that,
but I doubt you'd see a problem with on the order of a half inch, and
maybe even a little more. If you've got long lengths of untwisted
wire hanging off the back of the keystone jack, you're asking for
trouble, though (usually I have jacketed wire nearly to the butt of
the jack).

HTH

 >
 > Thanks,
 >
 > Roscoe
 >


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CJT wrote:

 > Roscoe Pendoscoe wrote:
 >
<snip>
  >>
  >>
  >> How much is too much, untwist-wise?
 >
 >
 > I try not to untwist any more than necessary; I think you can achieve
 > under 3/8 inches. I frankly don't know whether there's a spec on that,
 > but I doubt you'd see a problem with on the order of a half inch, and
 > maybe even a little more. If you've got long lengths of untwisted
 > wire hanging off the back of the keystone jack, you're asking for
 > trouble, though (usually I have jacketed wire nearly to the butt of
 > the jack).
 >
 > HTH

FWIW, I was at a book store today and encountered a huge tome called
(as I recall) the Network Cabling Handbook, which addresses this
issue; it says the untwisted portion should not exceed half an inch.

 >
  >>
  >> Thanks,
  >>
  >> Roscoe
  >>
 >
 >


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